A three-dimensional integrated circuit (3DIC) is a structure in which two or more layers of active electronic components may be integrated both vertically and horizontally in a single chip. Three-dimensional circuit architectures may enable, for example, the integration of logic devices, memory units, RF devices, optoelectronic devices, and microelectromechanical systems (MEMS) on a single chip. In a 3DIC, a plurality of device layers may be formed over a substrate, where each of the layers includes one or more semiconductor devices (e.g., one or more transistors). The device layers may be vertically separated from each other by interlayer dielectric layers or other interlayer layers.